Green mineral pigment



Patented Dec. 13, 1932 UNITED STATES PATENT OFFl FABBENINDUSTRIE nmr AKTIENGESELLSGHAFT, OI FRANKFORT-ON-THE-MAIN, GER- GRE EN MINERAL PIGMENT1T- Drawing. Application filed November 5, 1931, Serial No 573,295, andin Germany November 6, 1930. i

v The present invention relates to green mineral pigments consisting ofmixed crystals.

I have found that mixed crystals consisting of from 5 to 75 per cent byweight of magnesium orthotitanate (Mg TiO at least 5 per cent of cobaltchromite (CoCr O and any remainder of a chromite of nickel. zinc or maesium are brilliant green mineral colors aving great fastness toalkalies, acids and light. Moreover, these pigment colors withstand hightemperatures so that they are particularly suitable as pigment colorsfor ceramic materials. The lsomorphous admixture of magnesiumorthotitanate with cobalt chromite has the effect of displacing thesomewhat bluish color of cobalt chromite towards pure green. By theisomorphous admixture of-one or more of the said other chromites withthe mixed crystals of cobalt chromite and magnesium orthotitanate, theconsumption of the expensive cobalt compound can be substantiallyreduced without the excellent tinctorial properties of the cobaltchromite-magnesium orthotitanate pigments sufiering any appreciabledeterioration.

.The mixed crystal pigments may be prepared by melting the components inthe desired proportion, orby heating together the oxides, hydroxides,carbonates or other compounds of the metals concerned which areconverted into oxides by heating. Comunds which are converted intooxides when eated in the presence of water, as for example titaniumchloride, may also employed as initial materials. 1

The following examples will further illustrate the nature of thisinvention but the invention is not restricted to these examples. Theparts are by weight. Example 1 For the preparation of a mixed crystal Icolor igment consisting of ((loltfgfllr o and ,TiO, in the molecularratio (CoMg) Cr O,:Mg,TiO ;=.4: 1

in which the proportion of Go Mg in the chromite is 1:3 and whichtherefore corresponds to the molecular composition 61 parts of chromiumoxide (Cr O are dissolved in the necessary amount of sulphuric acidwhereupon 28 parts of cobalt suiphate, 123 parts of crystallizedmagnesium sulphate and 8 parts of titanium dioxide are added to thesolution. The 'mixture is then evaporated to dryness, ground and heatedto red heat for about 3 hours whereby the sulphuric acid is volatilized. A] very finegrained brilliant green pigment/is obtained which has avery good fas'tness to acids, alkalies and light.

' Example 2 For the preparation of a mixed crystal color pigmentconsisting of (Co,Zn)Cr O and Mg TiO in the molecular ratio 1: 1 inwhich the proportion of CQzZn' is 1:1 and which, therefore, correspondsto the molecu-- lar composition CoCr O :'ZnCr,O Mg TiOg-fl 1: 2.

Example 3 K For the preparation. of a mixed crystal color pigmentconsisting of,

and Mg Tio, in the molecular ratio 4: 1 in which the proportion of themetals in the chromite. is Co:Ni:Mg==1:1:6 and which, therefore,corresponds to the molecular composition GOCI O Nicl3o MgChO;

61 parts of chromium oxide (C50,) are dissolved in the nccessaryamountof sulphuric acid whereupon 14 partsof cobaltsulphate, 14 parts ofnickel sulp ate, 123 parts of crystallized magnesium sulphate and 8parts of titanium dioxide are added to the solution.

The mixture is then evaporated to dryness, ground and heated to red heatfor about 3 hours. The pigment thus obtained is similar to thatdescribed in Example 1.

lVhat I claim is 1. As new articles of manufacture pigment colorsconsisting of from 5 to per cent by weight of magnesium orthotit-anate,at least 5 per cent b weight of cobalt chromite and any remain er up toper cent of a chromite of a metal selected from the group consisting ofnickel, zinc and magnesium.

2. As new article of manufacture the pig ment. color consisting of mixedcrystals of cobalt chromite, magnesium chromite and magnesiumorthotitanate in the molecular ratio 1: 3: 1.

3. As new article of manufacture the pigment color consisting of mixedcrystals of cobalt chromite, zinc chromite and magnesiiun orthotitanatein the molecular ratio 1: 1:2.

4. As new article of manufacture the pigment color consisting of mixedcrystals of cobalt chromite, nickel chromite, magnesium chromite andmagnesium orthotitanate in the molecular ratio 1: 1: 6: 2.

In testimony whereof I have hereunto set my hand.

HANS WOLFF.

